Radio receiver adapted to monitor warning signals

Claim 2

A radio receiver comprising in combination: a. a first device having tuning means for selectively detecting the transmission of a plurality of audio frequency modulated radio frequency carrier signals of different carrier frequencies, said device having a first circuit for demodulating said signals, a second circuit connected to said first circuit to amplify the demodulated signals, and audio output means connected to said second circuit; b. a second device fixedly tuned to detect only an audio frequency modulated radio frequency carrier signal transmitted at a preselected fixed carrier frequency, said second device havinG another circuit for demodulating the signal transmitted at such fixed frequency, and a power amplification stage connected to said another circuit for producing an output signal proportional to the detected fixed frequency signal; and c. a power supply with on-off switch for energizing said first and second devices, and d. switching means connected between said first device and said power amplification stage and switchable only in response to the production of an output signal by said power amplification stage, said switching means including a two-position switch, said switch being in a first position in the absence of an output signal by said amplification stage, said switch being in a second position when said switching means receives said output signal, said switch in said second position providing a power lead from said power supply bypassing its on-off switch to energize said first device, and said switch in said second position also applying the signal transmitted at the fixed frequency to said second circuit and blocking the transmission of signals from said first circuit to said second circuit.

Claim 3

A radio receiver comprising in combination: a. a first device having tuning means for selectively detecting the transmission of a plurality of audio frequency modulated radio frequency carrier signals of different carrier frequencies, said device having a first circuit for demodulating said signals, a second circuit connected to said first circuit to amplify the demodulated signals, and audio output means connected to said second circuit; b. a second device fixedly tuned to detect only an audio frequency modulated radio frequency carrier signal transmitted at a preselected fixed carrier frequency, said second device having another circuit for demodulating the signal transmitted at such fixed frequency, and a power amplification stage connected to said another circuit for producing an output signal proportional to the demodulated audio frequency information; c. a power supply with on-off switch for energizing said first and second devices d. switching means movable from a first to a second position in response to an output signal received from said power amplification stage; and e. a third circuit connected in series between said another circuit and said first and second circuits only when said switching means is in said second position, said switching means in said second position completing a power supply circuit for said first device bypassing said on-off switch of said power supply, whereby, when said second device detects a transmission of a signal at the preselected fixed carrier frequency, said switching means is moved to said second position and the transmission of signals between said first and said second circuits is suppressed, and the demodulated signal received from said another circuit is amplified in said second circuit and emitted from said audio output means.

Claim 4

A radio receiver comprising in combination: a. a first device having tuning means for selectively detecting the transmission of a plurality of audio frequency modulated radio frequency carrier signals of different carrier frequencies, said device having a first circuit for demodulating said signals, a second circuit connected to said first circuit to amplify the demodulated signals, and audio output means connected to said second circuit; b. a second device fixedly tuned to detect only an audio frequency modulated radio frequency carrier signal transmitted at a preselected fixed carrier frequency, said second device having another circuit for demodulating the signal transmitted at such fixed frequency, and a power amplification stage connected to said another circuit for producing an output signal proportional to the demodulated audio frequency information; c. a power supply with on-off switch for energizing said first and second devices d. switching means movable from a first to a second position in response to an output signal received from said power amplification stage; and e. a third circuit connected in series between said another circuit and said first and second circuits only when said switching means is in said second position, said switching means in said second position completing a power supply circuit for said first device bypassing said on-off switch of said power supply, whereby, when said second device detects a transmission of a signal at the preselected fixed carrier frequency, said switching means is moved to said second position and the transmission of signals between said first and said second circuits is suppressed, and the demodulated signal received from said another circuit is amplified in said second circuit and emitted from said audio output means.

Claim 5

A radio receiver as defined in claim 2, wherein said another circuit includes a diode.

Claim 6

A radio receiver as defined in claim 2, wherein said third circuit is operatively shorted out when said switching means is in said first position.

Claim 7

A radio receiver as defined in claim 2, wherein one circuit of the connection between said first circuit and said second circuit includes said switching means in said first position.

Claim 8

A radio receiver as defined in claim 2, wherein said third circuit includes a parallel connection of capacitor and resistor across which a direct current voltage is developed and the demodulated signal in said second device is superimposed on the direct current voltage.

Claim 9

A combination as in claim 6, wherein the direct current component is developed across a condenser in the connection between said first circuit and said second circuit to bias said first circuit to cut off.

Claim 10

A combination as in claim 6, wherein the demodulated signal component is applied to an input resistor of said second circuit and the demodulated signal is amplified in said second circuit.

Claim 11

A combination as in claim 8, wherein said third circuit includes a potentiometer whereby the volume of the demodulated signal emitted from said audio output means can be varied.